The scientific investigations within this Specialized Center of Research in Transfusion Medicine seek to a.) contribute to the more efficient use of blood transfusions by developing methods for characterizing and evaluating transfusion practice; b.) assess the adequacy and accessibility of the national blood resource as an aid to planning national policy; c.) expand knowledge on the virology and serological identification of the retroviruses, HIV-1, HIV-2, HTLV-I and HTLV-II, which pose the most serious threat to transfusion safety; and pursue mew avenues to understanding the mechanisms by which HIV-1 attacks the immune response and hematopoietic systems. The research program is mounted via five major projects, each of which is designed to contribute to the overall objectives. One project makes use of abstracted patient hospital records, including transfusion records, to study which patients are transfused, and with how much blood and blood product. In this same project, national surveys of blood collections and transfusions are planned. In a second project, the goal is to develop and refine laboratory tests which will detect HIV-2 and HIV-1 as efficiently and specifically as possible; emphasis will be placed on detecting new closely related retroviral agents which might be contaminating the blood supply. In a related effort, the goal is to identify antigenic markers for screening for HTLV-II one of two known Human T Cell Leukemia viruses, thus providing the basis for a test to screen the blood supply. A fourth project seeks to identify the defect in antigen triggered activation of CD4+ T cells in HIV-1 infection in the defect in children with AIDS, including a group of hemophiliacs; thus providing a better understanding of the immunodeficiency in AIDS and laying foundations for rational approaches to therapy. The fifth study aims to dissect the cellular and viral factors which determine the HIV tropism for blood cells, thus providing new insight into the pathogenesis of HIV-1 related anemia. Among the patient groups being studied are a cohort of AIDS patients and their sexual partners; and a new cohort of children with AIDS, including hemophiliacs and children infected in utero and at birth.